Editing PDP-11/34 (section)

=== Backplane and Unibus ===
The DD11-PK is a 9-slot hex backplane. Slots 1 and 2 are wired for the processor; the rest mix standard Unibus slots, modified Unibus slots for memory and small peripheral controller (SPC) slots. The DD11-DK is the same backplane without the dedicated processor slots, used for expansion, and the DD11-CK is a 4-slot expander.<ref name="ug4" /> Power reaches each backplane through two 15-pin and one 6-pin Mate-N-Lok connectors from the power supply's distribution board.<ref name="ug4" /> Each unused SPC slot needs a G727 grant continuity card in connector D, or the bus grant chain is broken.<ref name="ug6" />

The KD11-E and KD11-EA have no Unibus termination of their own, which is why an M9301 terminator with bootstrap ROM must sit at the processor end of the bus and an M9302 at the far end.<ref name="ug1" /><ref name="chw" />